Motor control



L EATON.

MOTOR CONTROL. nmcmounun DEC.26, 1919.

1,434,689. I mm. 7,1922.

lnvbntori John Eaton, b fzwrq. M

His Attorney.

Patented Nov. 7, 1922 UNITED STATES JOHN EATON, OI SCHDNECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

MOTOR CONTROL.

Application filed December 26, 1818. Serial No..347,292.

To all whom it may com-em I 'Be it known that I JOHN EATON, a subject of the King of Great Britain, residing at Schenectady,in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Motor Controls, of which the following is a specification.

My invention relates to an improved motor control and it provides im roved means whereby the motors are starte and stopped and are generally controlled in a safe, rehable and efficient manner. More specifically, my invention relates to the control of the driving motor or motors for a machine having an element which is reciprocated by re versing the motor.

Although not limited to such use, my invention has a particular applicationin electric motor drives for planers or the like. Arran ements of this general nature have hereto ore been provided in which an electromagnetic switch or contactor is provided for energizing the motor from the source of supply for each direction of operation, the forward and reverse contactors being interlocked in such a wa that each contactor is prevented from closing unless the other has opened. In such an arran ement it occasionally happens that one, 0 the contactors fails to 0 en when its windin is deenergi'zed so t at the planer or ot er machine element will continue to operate in one direction and thereby cause serlousdamage. One of the objects of my invention is to prevent such an occurrence by instanta-' neously stopping the motor upon the failure of the contactor to my invention in one cm I so arrange the parts that, even though a contactor fails to open, the contactor for the reverse direction will nevertheless close thereb causing a dry; namic braking circuit for t e motor to established to instantaneously stop the motor.

Fora better understanding of my invention, reference is had to the accompanying drawin wherein I have shown my invention em odied in concrete form for purposes of illustration. In the single figure, which in simplified form, diagrammatically illustrates the embodiment of my invention, the electric motor having an armature A and open. In carrying out responsively to the motor armature voltage is adapted to close and include the braking resistance R in the motor armature circuit so as to bring the motor to rest quickly when either contactor is opened and before the other contactor is closed.

The windings of the contactors F and R are'controlled by means of a master or pilot switch S, the arran ment being such that when the switch is thi 'own to the lower positlon the contactor F is energized to close, and when thrown to the upper position the contactor R is energized to close. A line switch or circuit breaker CB is provided for connecting the motor and its control equipment to the source of supply. This circuit breaker is adapted to be closed in any suitable manner and is adapted to be opened in response to either an overload by means of an overload coil which tri s the pivoted latch 10, or in response to a ailure of voltage, thereby breaker to open in accordance with its bias to the open position. Interlocks 11 and 12 areprovided on the circuitbreaker for connectlng the shunt field of the motor to the motor armature terminals and connecting the motor armature in a d namic brake circuit with a portion of t e resistance R. The arrangement is such that when the curexcess of a predetermined value, or the voltage of the source of supply is less than a predetermined value, the circuit breaker will be automatically opened and the motor auto matically connected in a dynamic brake circuit of low resistance so that the motor will permitting the circuit ioo interlock 15 is provided for i rent flowing through the series coil 13 is in l locking arrangement between the-contactors F and R, so that it is possible for the one -contactor to be closed even though the other contactor be maintained closed, as for instance in case the contact tips of this other contactor should be welded together and the contacts remain closed even through the contactor winding is deenergized.

As thus constructed and arranged, the operation of my invention is as follows: The circuit breaker CB will first be closed, and assuming that it is desired that the motor operate in the forward direction, the master switch S will be thrown to its lower 'posi tion. so as to energize the contactor F to closeand connect the motor armature to the [source of supply.

' connected to the'sourceof suppl by theclosing The shunt field f was of the circuit breaker. ssuining 'now t at the motorhas driven the planer or. other machine in the forward direction I and that it is desired that the machine be reversed, this will be accomplished by throw-5 ing the master switch toits upper position,thereby energizing the winding of the QCOII t B JCtQI R. ,The brake contactor B will b -e'nergized to -close during the interval be- ".'tween the-deenergization of the winding of contactor; Fahd the .energization of'the l will close; connectingthe motor armature in windingof'contactorR, and the contractor B a dynamic brake. circuit with; the resistance .JR". With brake ms-car, closed, the

"- .freversing contactor cannot close'until the motor has" b en; very-"materially reduced in speed, since thegpivoted mechanical interlock ac'ontact'o'r. R open even though "the K this contactor is en- Y ergizedj- As asjthe speed ofthe motor has 'eroppea-w theipredetermined value, the

' contactorR: will "close; thereby reversingjthe connection.-. of; the 'imit'or: "-armature. to the sourcq'oi supply "an energizing the motor.

' reversing :the im'ot'or for operatiohfl 'jth" posits direction. In

the forward-filirectiomthe hrak efcontactor B will close to establishsth "dynamic brake cir' cuit in 'the samsymaa ri as that explained "in connectionfiwiththereversal from the -f orvward directiomto' ,di'rectiong j In 'casegflfor. any "reason the; contact'orfF' shouldTremainTrlosed, d forf instance to;

I "',masten switchfiiromthegl contactor is; deen'ergized b 0 er position, brake 'contactor Manet be "able I close sir-ice it" is f-mechanicallyrheld open I driven driven-m ths forward direction -and' af-EseriQ; .ous cond t on result.- However; my! .arrangementi whemthe'one Scontactor st cks,

the" other, contactor" which provided'ifor reversing thesmotor'may be closed. Thus;

.disc 11..

brought to rest very quickly, andan accident :this direction to i its "contacts, orifor 1 evenit possible thatwhen the contacts of x the} pnej contactorstick and'jthe. other/ contactor mdrinwaockir machine .dynamic braking circuit for the motor through the contact disc 12 and a portion of the resistance R, the field being connected to the motor armature through the contact The motor will thereupon be to the machine driven by the motor thereby prevented. The same operation will occur in case the contactor B should stick when it is attempted to energize {the motor for operation in the forward direction after an operation in the return direction. Thus, the

so i

forward contactor will be permitted to close, short circulting the source of supply, in-

'cluding the motor in a dynamic brake circuit and automatically opening the'overload circuit breaker, including the motor in an additional dynamic brake circuit.

It will be observed that a dynamic brake circuit. is established when both contactors close, independently of that established by the circuit' breaker GB in its open'position. Thus, :in case the 'forward contactor should remain closed and the reversing contactor closed, the motor armature is connected in a;

local dynamic'brake circuit of low resist ance, the dynamic brake circuit including both'contacts of each switch. Thus, one dynamic brake circuit is through the lower contact of'switch R, the conductor '16, conductor'1-7, and. upper contact of switch F. Another dynamic brake circuit is also-closed,

which includes the upper contact of switch R, conductor 18, conductor 19, and the lower contact of switch F. The motor fieldwill in this case beconnected across-the, motor a'rmature,-and although the field is short circuited through the contacts of contactors F and R, thisfield will continue to be energized' for'an interval suflicient to bring the 'motor'to "rest 'becausof the inductance of the field; The inductance of, the forwardv andf-reversing'contactor electromagnets will *alsojcausethe last" contactorfto be closed to be maintained, closed j for-- an interval. How

.is'-{clo' sed,' thus establishing vashort circuit the; contacts of the last contactor to-close will bejwjelded shut. "This-is preferable tog having. "the motor operate the driven "machine beyond the predetermined limits- 1. The oil cuit breakerf CB isnot 'necessa'ry.v "for the opgerationfof Qmy'IinVention and" an ordinary 4 over-load circuitbreaker or fuse or" othermeans may be provided for'disconnecting. the motor from the sourceyof supply when' the source of supply is short circuited by the ClOSlIlo of both contactors.

What I claim as new and desire to secure by Letters Patent of the United States, is:

1. The combination in a system of motor control of means for connecting the motor to a source of supply for opposite directions of rotation comprising Y an electromagnetic switch for each direction and a reversing switch for controlling the same, a brake for the motor adapted to be applied during the interval between the opening of one switch and the closing of the other, means for preventing the apnlication of the brake in case either switch is closed, and means whereby upon the failure of one of said electromagnetic switches to open upon the energization of the other by the reversing switch, a dynamic braking circuit for the motor is established.

2. The combination in a system of motor control, of a pair of switches, one for connecting the motor to a source of supply for operation in one direction and the other for connecting the motor to the source for operation in the reverse direction, means for automatically establishing a dynamic brake circuit upon the opening of either electromagnetic switch and for preventin the closing of the said brake circuit unless oth switches are 0 en, and means whereby closing the one switc 1 with the other switch closed establishes a dynamic braking circuit for the motor for bringing the motor quickly to rest.

3. The combination in a system of motor control of a pair of switches, one for connecting the motor to' a source of supply for operation in one direction and the other for connecting the motor to the source for operation in the reverse direction, a dynamic brake circuit, means for automatically establishing the same during the interval between the opening of either switch and the closing of the other, means for preventing'the establishment of said brake circuit 1n the case either switch is closed, and connections whereby the closin 'of one switch with the other switch close establishes another dynamic mally open dynamic brake circuit and means forautomatically closing the same during the interval between the opening of one switch and the closing of the other switch, means for preventin the closing of the brake circuit when eit er switch is closed, a master switch for controlling the windings of said switches, the said master switch hav- -ing two operative positions at each of which the winding of one switch is energized and the winding of the other switch 1s deenergized, and connections whereby closing one electromagnetic switch includes the motor in a dynamic brake circuit provided the other switch does not open.

5. The combination in a system ofwmotor control, of a pair of electromagnetic switches,

one for connecting the motor to a source of supply for operation in one direction and the other for connecting the motor to the source for operation in the other direction, a master switch for controlling the windings of said switches, the said master switch having ti o operative tpositions at each of which t e winding 0 one switch is energized and the winding of the other switch is deenergized, a circuit breaker having means for automatically opening the same and includin the motor in a dynamic brake circuit, an connections whereby closing one electromagnetic switch rovided the other electromagnetic switch 'oes not open includes the motor in a dynamic brake circuit through the contacts of both electromagnetic switches, and causes the circuit breaker to automatically open and establish another dynamic brake clrcuit. I

In witness whereof, I have hereunto set my hand this 23rd day of December, 1919. JOHN EATON. 

